1. Field of the Invention
The present invention relates to a liquid crystal display module, and more particularly to a backlight assembly for use of liquid crystal display (LCD) module, which is enhanced for a better luminance.
2. Description of the Related Art
Cathode ray tubes (CRTs) are primarily used for monitors of televisions, measuring instruments, or data terminals. However, such CRTs are large and heavy, and thus inappropriate for a tendency of size and weight reductions in the electronic appliances.
Liquid crystal display (LCD) devices are a well known form of flat panel display. Especially, the smaller, lighter and less power consumptive characteristics make the LCD devices considered as one of the most leading display devices for overcoming disadvantages of CRTs.
Differently from CRTs, the liquid of an LCD device which is injected between a thin film transistor (TFT) substrate and a color filter is not a light emitting element but a light receiving one that controls the amount of the light emitted from external devices so as to display onto a screen. Therefore, an additional light source, say, backlight unit, is absolutely necessary for irradiating the light onto the LCD panel.
Accordingly, performance of the backlight unit affects significantly to the quality of LCD devices.
Such a backlight unit is composed of various optical components.
As shown in FIG. 1, to prevent the LCD panel from being suffered from the lowered efficiency of the light, which may occur while the light is emitted to the LCD panel, the backlight unit employs a lamp cover 24 for covering the outer periphery of a fluorescent lamp 18, and a back cover 28 for supporting the lamp cover 24.
However, as shown in FIG. 1, if the lamp cover 24 and the back cover 28 contact at whole surfaces thereof, the heat which is generated when the lamp is turned on is transmitted to the back cover 28 through the lamp cover 24. Accordingly, the time period for luminance saturation is delayed by the heat loss.
As expressed in the following Equation (1), a capacitor is in proportion to the size (S), and is in inverse proportion to the distance (L). ##EQU1##
Wherein, C indicates the capacitance, .sigma. indicates the dielectricity, S indicates the size of the contact area between conductors, and L indicates the distance between conductors.
However, the distant-L1 between the lamp cover 24 and the back cover 28 is just 0.05 mm, which increases size (S) of the contact area between the lamp cover 24 and the back cover 28 during assembly. As a result, the value of the capacitance (C) becomes larger, which causes an increase in current leakage and lowering of the luminance. In addition, the size of the contact area increases, thus extending the time period for luminance saturation.
When the SIC-130 inverter is used in the simulation, the estimated luminance is approximately 100 nit at the current of 5 mA, the current leakage is approximately 1.25 mA, and the time period for luminance saturation is 40 to 50 minutes.
Moreover, the luminance of the lamp of the backlight unit varies in accordance with the ambient temperature. The luminance of the lamp becomes the highest when the ambient temperature is about 40.degree. C. to 50.degree. C. However, the back cover is made of a metal, which emits a heat. Thus, the temperature around the lamp is dropped down and the luminance is lowered.